The present invention relates to a magnetic circuit for inductive electrical devices. Such inductive electrical devices include both reactors and transformers.
Inductive electrical devices such as reactors and transformers contain a core of laminated, soft-magnetic sheet which forms one or more closed magnetic circuits for the magnetic flux. The core consists of two yokes with legs arranged between the yokes, around which legs windings are arranged. When the core (preferably in reactors) is made in the form of a frame of straight sheet strips, it is generally desirable that this frame in layer upon layer have the same width in all the frame parts, so that the magnetic flux is able to easily run around in the frame without having to be redistributed between different layers by passage from layer to layer. Such cross-passage of flux means that the flux will have to pass through plane sheet surfaces, which causes great additional losses at the sheet surfaces and causes undesirable heating of the core.
In certain cases, however, it is possible for mechanical reasons to construct the different parts of the core with different shapes of cross-sectional area in spite of the fact that the cross sectional area is maintained substantially constant. It may thus be desirable to make the core leg with substantially round cross-section in order for it to be better surrounded by a circular winding coil, whereas the yokes are constructed with a rectangular cross-section.